Chapter 10 EARTHLIKE PLANETS: VENUS AND MARS

An Ocean on Mars?

Much of the northern part of Mars may have once been covered by an ocean, according to NASA scientists

Lowell's Mars Globe.

One of the remarkable globes of Mars prepared by Percival Lowell, showing a network of dozens of canals, oases, and triangular water reservoirs that he claimed were visible on the red planet.

Phobos: Doomed Martian Moon

Phobos is only 14 miles across and Deimos is 8 miles across. Mars has two small moons, Phobos and Deimos. Phobos is so close to Mars (≈ 6000 miles) that tidal forces will likely tear it apart at some future time and turn it into a ring around Mars.

Martian Atmosphere

The Martian atmosphere is mainly CO2 (95%) with small amounts of N2 (2%), argon (2%) and traces of oxygen and water. The atmosphere's pressure is about 1% that of the Earth's. The detailed mechanisms by which Mars has lost its atmosphere are currently being studied by a NASA spacecraft (MAVEN). However, it seems clear that the low Martian surface gravity (38% of Earth's) and the lack of a magnetic field (to protect the atmosphere from the solar wind) have played major roles.

Venus, unlike the Earth cont:

The atmosphere of Venus is 96% CO2, 3.5% N2, and small amounts of H2O and other gases. This atmosphere is very dense or thick, with pressures 90 times higher than on Earth. The clouds of Venus that obscure its surface are mostly sulfuric acid droplets! These conditions cause a very large greenhouse effect on Venus, with an average temperature of 730 K (≈ 860°F). This is hotter than the maximum temperature on Mercury (700 K), even though Mercury is closer to the Sun!

Mars Map from Laser Ranging.

These globes are highly precise topographic maps, reconstructed from millions of individual elevation measurements made with the Mars Global Surveyor. Color is used to indicate elevation. The hemisphere on the left includes the Tharsis bulge and Olympus Mons, the highest mountain on Mars; the hemisphere on the right includes the Hellas basin, which has the lowest elevation on Mars.

Impact Craters on Venus.

These large impact craters are in the Lavinia region of Venus. The largest of these craters has a diameter of 50 kilometers. It would take a rather large impactor to make it through the thick Venusian atmosphere to the surface.

Wind Erosion on Mars.

These long straight ridges, called yardangs, are aligned with the dominant wind direction. This is a high-resolution image from the Mars Reconnaissance Orbiter and is about 1 kilometer wide.

Pancake-Shaped Volcanoes on Venus.

These remarkable circular domes, each about 25 kilometers across and about 2 kilometers tall, are the result of eruptions of highly viscous (sludgy) lava that spreads out evenly in all directions

Surface of Venus.

These views of the surface of Venus are from the Venera 13 spacecraft. Everything is orange because the thick atmosphere of Venus absorbs the bluer colors of light. The horizon is visible in the upper corner of each image. For a time, the Soviet Union specialized in landing spacecraft on Venus. These were specially designed to withstand the enormous pressures and temperatures on the surface. One of them lasted for two hours, the others less. NASA has specialized in spacecraft that orbit Venus and use radar to map the surface.

Percival Lowell (1855-1916).

This 1914 photograph shows Percival Lowell observing Venus with his 24-inch telescope at Flagstaff, Arizona. He said that he could see canals on Mars.

Spirit Rover on Mars.

This May 2004 image shows the tracks made by the Mars Exploration Spirit rover on the surface of the red planet. It wore out and ceased operating in 2010.

Why is the Earth's atmosphere not mostly CO2 like that of Mars and Venus?

because, we have plants that do photosynthesis

How would one know that this meteorite is from Mars?

you put a chunk of mars into a vacuum system and you pump all of the air out of it you reduce the pressure of a factor of 1 million you break the chunk and inside there are pockets of air and with the instrament that messures what gasses comes out of the little pockets of air you get an exact match of the marshan atmosphere.

Mars near Opposition

A very advanced amateur astronomy photograph of Mars when it was near the Earth. Note that the north polar cap and some clouds are visible. Mars has half the diameter of the Earth and one tenth of its mass. Its density is 3.9 g/cc, implying that it has a small iron core. The temperature can get up to about 70°F (20°C) near the equator. It drops to about -100°F (-70°C) at night. One Martian day is 40 minutes longer than one Earth day. The orange-colored areas are where wind has deposited iron-oxide dust (rust). Theia is thought to have been about the size of Mars

First ever close-up pictures of Mars - in 1965 Where are the canals?

After an eight-month voyage to Mars, NASA's Mariner 4 spacecraft made the first flyby of the red planet, becoming the first spacecraft to take close-up photographs of another planet. The images show lunar-type impact craters. A television camera onboard took 22 pictures, covering about 1% of the planet. Initially stored on a 4-track tape recorder, these pictures took four days to transmit back to Earth. there is no canals

The Terrestrial Planets - Mercury, Venus, Earth and Mars

Are all relatively close to the Sun - too warm to have captured large amounts of hydrogen like the outer gas giant planets. Thus, these are all "rocky" planets, also called terrestrial planets. Terra means "earth" in Latin. These planets have very few moons. The Earth has "the Moon" and Mars has two very small moons, which are probably captured asteroids.

Olympus Mons.

The largest volcano on Mars, and probably the largest in the solar system, is Olympus Mons, illustrated in this computer-generated rendering based on data from the Mars Global Surveyor's laser altimeter. Placed on Earth, the base of Olympus Mons would completely cover the state of Missouri; the caldera, the circular opening at the top, is 65 kilometers across, about the size of Los Angeles.

Why Doesn't Venus Have a Moon?

The reverse (retrograde) spin of Venus was caused by it being hit by something large. The collision didn't cause a moon to form around Venus because it apparently did not hit at a glancing angle. However, the collision of Theia with Earth was glancing, created the Moon, and sped up the rotation of the Earth.

Face on Mars.

The so-called "Face on Mars" is seen (a) in low resolution from Viking (the "face" is in the upper part of the picture) and (b) with 20 times better resolution from the Mars Global Surveyor

Radar Map of Venus.

This composite image has a resolution of about 3 kilometers. Colors have been added to indicate elevation, with blue meaning low and brown and white high. The large continent Aphrodite stretches around the equator, where the bright (therefore rough) surface has been deformed by tectonic forces in the crust of Venus.

Martian Meteorite.

This fragment of basalt, ejected from Mars in a crater-forming impact, eventually arrived on Earth's surface.

Valles Marineris ("Mariner Valley")

This giant valley apparently formed as a crack in the Martian surface as the planet cooled. It is over 3000 km long and up to 600 km wide, many times larger than the Grand Canyon. It was named after the Mariner spacecraft.

Gullies on the Wall of Garni Crater.

This high-resolution image is from the Mars Reconnaissance Orbiter. The dark streaks, which are each several hundred meters long, change in a seasonal pattern that suggests they are caused by the temporary flow of surface water.

Water Frost in Utopia on Mars.

This image of surface frost was photographed at the Viking 2 landing site during late winter.

Martian North Polar Cap.

This is a composite image of the north pole in summer, obtained in October 2006 by the Mars Reconnaissance Orbiter. It shows the mostly water-ice residual cap sitting atop light, tan-colored, layered sediments. Note that although the border of this photo is circular, it shows only a small part of the planet. Here we see a small section of the layered terrain near the martian north pole. There is a mound about 40 meters high that is sticking out of a trough in the center of the picture.

Ridges and Cracks.

This region of the Lakshmi Plains on Venus has been fractured by tectonic forces to produce a cross-hatched grid of cracks and ridges. Be sure to notice the fainter linear features that run perpendicular to the brighter ones. As this is a radar image, the brightness of the ridges indicates their relative height. This image shows a region about 80 kilometers wide and 37 kilometers high. Lakshmi is a Hindu goddess of prosperity.

Gale Crater.

This scene, photographed by the Curiosity rover, shows an ancient lakebed of cracked mudstones. Geologists working with the Curiosity rover interpret this image of cross-bedded sandstone in Gale crater as evidence of liquid water passing over a loose bed of sediment at the time this rock formed.

Venus as Photographed by the Pioneer Venus Orbiter.

This ultraviolet image shows an upper-atmosphere cloud structure. In visible light, the clouds are featureless. Note that there is not even a glimpse of the planet's surface. The clouds of Venus completely obscure its surface from visible light.

Daytime Moon Meets Morning Star

Venus is the brightest planet visible in the sky

Venus has some Earth-like similarities

Venus orbits closer to the Sun than the Earth. It is slightly smaller (7521 miles vs 7926 miles). It's surface gravity is 91% that of the Earth. Its density is 5.2 g/cc, implying that it has a substantial iron core, like the Earth. The interior structure is believed to be similar to that of the Earth, with a rocky mantle. From studies of the surface, it is clear that Venus has volcanos and plate tectonics.

Venus, unlike the Earth

Venus orbits the Sun every 225 Earth days. It takes 243 Earth days to spin on its axis. It spins very slowly "backwards" on its axis from the direction of the spins and orbits of the other planets. This is presumably from a collision with a large object early in the history of the Solar System.

Sky Over Great Salt Lake

Venus up and to the left of the Moon, Jupiter up and right of the Moon. An aircraft to the far right. APOD Nov 8, 2015

Evaporating Ice on Mars.

We see a trench dug by the Phoenix lander in the north polar region four martian days apart in June 2008. If you look at the shadowed region in the bottom left of the trench, you can see three spots of ice in the left image which have sublimated away in the right image.

Victoria Crater.

a. This crater in Meridiani Planum is 800 meters wide, making it slightly smaller than Meteor crater on Earth. Note the dune field in the interior. b. This image shows the view from the Opportunity rover as it scouted the rim of Victoria crater looking for a safe route down into the interior.

what is this? slide 16 picture

surface of mars

Venus' Atmosphere.

the layers of the massive atmosphere of Venus shown here are based on data from the Pioneer and Venera entry probes. Height is measured along the left axis, the bottom scale shows temperature, and the red line allows you to read off the temperature at each height. Notice how steeply the temperature rises below the clouds, thanks to the planet's huge greenhouse effect.